1. Field of the Invention
The present invention relates to intraluminal prostheses for implantation into a mammalian vessel, and in particular, to intraluminal stents that do not experience foreshortening in the longitudinal direction when the stent is deployed to an expanded state.
2. Description of the Prior Art
Intraluminal prosthesis, such as stents, are commonly used in the repair of aneurysms, as liners for vessels, or to provide mechanical support to prevent the collapse of stenosed or occluded vessels. These stents are typically delivered in a compressed state to a specific location inside the lumen of a vessel or other tubular structures, and then deployed at that location of the lumen to an expanded state. These stents have a diameter in their expanded state which is several times larger than the diameter of the stents in the compressed state. These stents are also frequently deployed in the treatment of atherosclerotic stenosis in blood vessels, especially after percutaneous transluminal coronary angioplasty (PTCA) procedures, to improve the results of the procedure and to reduce the likelihood of restenosis.
U.S. Pat. No. 5,733,303 (Israel et al.) and U.S. Pat. No. 5,827,321 (Roubin et al.) describe the problems associated with the foreshortening of intraluminal stents when such stents are expanded. In addition, U.S. Pat. No. 5,733,303 (Israel et al.) describes stents that have struts whose longitudinal length decreases when the stent expands, thereby causing the overall longitudinal length of the stent to foreshorten. These struts are connected by flexible connecting members, each having an area of inflection that functions to compensate for the foreshortening experienced by the struts during expansion of the stent.
Unfortunately, there are certain drawbacks associated with providing flexible connecting members that have areas of inflection. First, to accomodate the areas of inflection, these connecting members often create segments within the stent where the aperture or opening defined by these connecting members have a large size. Such increased aperture size may allow increased ingrowth of tissue (also known as “in-stent restenosis”). Second, curved areas of inflection on these connecting members may cause distortion of the lumen of the stent when the stent is twisted or experiences angulation in the longitudinal direction. Third, the connecting members form an area of weakness in the stent structure which may encourage kink of the stent at the site with flexion or angulation, or which in extreme circumstances may lead to stent breakage after experiencing repetitive stress. In other words, the provision of the connecting members decreases the amount of support that the stent can enjoy.
Thus, there still remains a need for an intraluminal prosthesis that maintains a consistent length in both its fully compressed and fully expanded states, while avoiding the disadvantages set forth above. There also remains a need for a stent which can accomodate body vessels having varying lumen diameters, different anatomies, and different disease states.